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Chapter 2: Cisco Internetwork Operating System (IOS) Fundamentals
Physical interfaces are referred to as
interfaces
by the IOS commands, as opposed to
ports
or
plugs
. IOS commands familiar on one platform will be familiar on another. Some nuances are
involved in numbering the interfaces, however. In some smaller routers, the interface number is
a single number. However, with some other families of routers, the interface is numbered first
with the slot in which the card resides, followed by a slash and then the port number on that
card. For example, port 3 on the card in slot 2 would be interface 2/3. Numbering starts with 0
for card slots and 0 for ports on any card. In some cases, the interface is defined by three
numbers: first the card slot, then the daughter card (typically called a port adapter), and then a
number for the physical interface on the port adapter. The 2600 and 3600 families also use a
slot/port numbering scheme.
In this book, the single-digit interface numbers are used simply for consistency and readability.
If you want to dig deeper, you might want to read about processors and interfaces in the Cisco
Product Catalog (http://www.cisco.com/univercd/cc/td/doc/pcat/).
Command-Line Interface
Cisco uses the acronym CLI to refer to the terminal user command-line interface to the IOS.
The term CLI implies that the user is typing commands at a terminal, terminal emulator, or
Telnet connection. Although you can pass the CCNA exam without ever having used the CLI,
actually using the CLI will greatly enhance your chances.
To access the CLI, use one of three methods, as illustrated in Figure 2-3.
Figure 2-3
CLI Access
User Mode
Console
Aux
IP Net
Telnet
Interfaces
ch02.fm Page 28 Monday, March 20, 2000 4:57 PM